Preparation of carbon nanomaterials through CH4 pyrolysis on (Co plus Mo)/MgO catalysts with different metal contents

We have studied the influence of active metal content in (Co + Mo)/MgO catalysts (0.5-5 wt % Co + Mo) on the morphology and properties of catalytic methane pyrolysis products (900A degrees C, CH4: H-2 volume ratio of 1: 1, pyrolysis time in the range 20-120 min). The results demonstrate that, in addition to the main pyrolysis product, carbon nanotubes, the process may yield graphene shells on MgO particles, graphene shells on relatively large Co particles, and amorphous carbon on carbon nanotubes. The metal content of the catalyst determines the relationship between different carbon species, their net yield, and the specific surface area (S) of the products. Increasing the pyrolysis time increases the S of the materials obtained at low metal concentrations in the catalyst, whereas on the catalyst containing 5 wt % metals S remains unchanged. In contrast, the yield of carbon nanomaterials is more sensitive to the pyrolysis time on the catalyst containing 5 wt % metals.